Tough to say. They're both cartoonishly evil, and both of them tend to have pretty high morale and do their best to put up a good fight, so it doesn't just feel like a one-sided stomp.

I'd imagine that Boko Haram would be in the running for #1, though, given that they've managed to inspire pretty unprecedented cooperation amongst different religious and ethnic and national groups, all coming together in peace and fraternity just to kill Boko Haram zealots.